<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>后盾人</title>
  </head>
  <body>
    <script>
      //null undefined
      // let config={} ;
      // let web = '';
      // function show(name) {
      //   console.log(name);
      // }
      // console.log(show());

      let a = 324;
      let b;
      console.log(typeof f);
      function star(num = 5) {
        num = num || 5;
        // if (num == undefined) {
        //   num = 5;
        // }
        for (let i = 0; i < num; i++) {
          document.write("*");
        }
      }
      star();
    </script>
  </body>
</html>
